1. Field of the Invention
The present invention relates to a pressure plate of a clutch cover assembly and a method for correcting rotational imbalances present in the clutch cover assembly by removing preformed portions of the pressure plate.
2. Description of the Related Art
A clutch cover assembly is used for selectively engaging and disengaging a clutch disc from contact with a flywheel. The clutch cover assembly includes a clutch cover fixed to the flywheel, a pressure plate disposed within the clutch cover and a biasing means for urging the pressure plate into contact with the flywheel. The biasing means could be, for instance, a series of coil springs or a diaphragm spring. The pressure plate is configured to engage the clutch disc and urge the clutch disc into contact with the flywheel. The biasing means are configured to bias the pressure plate toward the flywheel.
The clutch assembly incorporating the clutch cover assembly described above rotates together with the flywheel. Due to the rotation of the flywheel and clutch cover assembly, it is important for the flywheel and clutch cover assembly to be balanced to prevent undesirable vibrations. Typically, the pressure plate is formed by cast molding and therefore, is relatively dense and requires balancing. Therefore, the pressure plate is often balanced separately from the clutch cover assembly.
The conventional method for correcting imbalances in the pressure plate includes forming a hole or holes somewhere on a surface of the pressure plate, often on a surface opposite a friction surface which engages the clutch disc.
As described above, since the pressure plate rotates together with the flywheel at a high speed, when the pressure plate is provided with the mechanical working process such as forming a hole/piercing, the mechanical strength of the processed portion thereof is degraded. Therefore, the extent of the correction of an imbalance in the pressure plate is limited due to potential degradation of the mechanical strength of the pressure plate. As a result, often final correction of imbalances in the pressure plate are effected not on the pressure plate itself but instead on the clutch cover assembly. Such corrections of imbalances of the pressure plate on the clutch cover assembly are not desirable since the pressure plate still includes some imbalance.